The invention relates to an indexable cutting insert which can be used for material-removing machining. The invention relates in particular to an indexable cutting insert which is of substantially polygonal shape in plan view and which, in a preferred embodiment, is of generally triangular shape.
FIG. 1 shows a known indexable cutting insert 10 which, as seen in plan view, has a generally triangular body with three cutting corners 12. Extending centrally through the indexable cutting insert is a passage opening 14 which serves for the fastening of the indexable cutting insert to a tool holder. The passage opening 14 is surrounded on both sides, which face away from one another, of the indexable cutting insert 10 by in each case one face 16, only the upper of which is visible in FIG. 1. A cutting edge 18, 20, 22 is formed at least in portions at the transition between the face 16 and a circumferential surface of the indexable cutting insert 10.
Of the cutting edges, the cutting edge 20 which is continuously curved is situated in the region of the cutting corners 12. The curved cutting edge 20 is adjoined on one side by the cutting edge 18 and on the other side by the cutting edge 22. These are both substantially straight. The two cutting edges 18, 22 are assigned flanks 24, 26. Said flanks extend in a plane which is oblique with respect to the central axis of the passage opening 14. In relation to the cutting edges 18 and 22 which are situated on one side and on the other side of the curved cutting edge 20 arranged at the front and on the right in FIG. 1, the flank 24 constitutes a negative flank, whereas the flank 26 is a positive flank. In other words, the flank 24 is inclined such that its top edge is at a smaller distance than its bottom edge from the central axis of the passage opening 14. This is reversed in the case of the flank 26.
For the curved cutting edge 20′ which is assigned to the face 16 not visible in FIG. 1, the angle of inclination of the flanks 24, 26 is exactly reversed: the flank 24 is a positive flank, and the flank 26 is a negative flank.
As a result of said arrangement of the flanks, the indexable cutting insert shown has six identical cutting geometries, specifically three on the “top side” of the cutting corners 12 and three on the “bottom side” of the cutting corners 12.
Between the curved cutting edges 20, 20′ which are arranged at one cutting corner 12 there extends a curved surface 28, the radius of curvature of which corresponds to the radius of curvature of the cutting edges 20, 20′. Owing to the differently inclined flanks 24, 26, the curved cutting edges 20, 20′ are offset with respect to one another if the central axis of the passage opening 14 is taken as a reference line. Therefore, in the exemplary embodiment shown in FIG. 1, the curved corner surface 28 runs not in the vertical direction but rather slightly obliquely from top right to bottom left. As a result, the main body of the indexable cutting insert cannot be produced in a single-piece press mold by uniaxial pressing. Even if use is made of slides which press in the radial direction against the circumferential surfaces of the main body of the indexable cutting insert where the flank 24 is generated, the main body cannot be removed from the mold owing to the oblique alignment of the corner surfaces 28.